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421 Error when sending email IP address is not permitted to send messages

Frequent Visitor

421 Error when sending email IP address is not permitted to send messages

Hi, I have 3 email programs (Windows Live Mail, Outlook, and Mail Bird) and just in the last 2 days, none of them can send Outgoing messages (Incoming emails are fine).  I've already talked to support and received no assistance.  Here's the error message.

 

An unknown error has occured.  Server Error 421  Server Response:  421 resomta-po-17v.sys.comcast.net

resomta-po-17v.sys.comcast.net CSI IP xxx.xxx.xx.xxx (with the actual numbers of course) is not permitted to send messages.

Please contact support if you feel this is in error.

Server: 'smtp.comcast.net' 

Windows Live Mail Error ID: 0x800CCC67

 

That IP address is NOT any of my devices...not my smartphone or computer...does anyone have an idea what I can do?  Thanks

 

New Poster

Re: 421 Error when sending email IP address is not permitted to send messages

I'm having exactly the same problem.  Just started earlier this week.  None of my sent mails have gone out.  The web portal works fine.  I suspect that the IP address is my router address, and it is being blocked by Comcast for some reason, but the support person I chatted with insisted that it was my email software configuration, not their server, since the webmail works. 

Frequent Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

Thank you for confirming that I'm not crazy...I have other computers with the same software configuration that have no problem.  It's only this one IP Address that Comcast is blocking...I'm going to keep calling Tech Support until I get someone with the knowledge of what's going on...if you finally get an answer, please let me know what it was!  Thanks!

 

Oh, you can open up a Command Prompt window and type in    ipconfig    then press the Enter key...that should give you the IP Address of your router...in my case, it's not that IP Address that they're blocking...

New Poster

Re: 421 Error when sending email IP address is not permitted to send messages

Thanks, I did verify that it is my IP address that they are blocking.  I'm going to see if my VPN will let me get around it, but I would like to hear from Comcast why they are doing it.

Frequent Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

Oops, the Command Prompt Ipconfig command will only give you your Local IP Address, NOT the Public IP Address which is what Comcast is blocking.  For that, go to:

 

https://www.whatismyip.com/

and you'll get your Public IP Address.  That IP Address will match what Comcast is blocking.

Expert

Re: 421 Error when sending email IP address is not permitted to send messages


@Mikeprofla1 wrote:

 

Oh, you can open up a Command Prompt window and type in    ipconfig    then press the Enter key...that should give you the IP Address of your router...in my case, it's not that IP Address that they're blocking...


FWIW, that output gives the private / non-routable LAN interface IP address that the router's DHCP server is assigning to the particular network clients and not the public / routable WAN IP interface address that the Comcast DHCP is assigning to the router / connection.



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Frequent Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

I realized that after I typed it..you used much more eloquent language than I did to explain it better...thanks...I'm 61 years old and don't remember all the technical terms any more!  HA!

New Poster

Re: 421 Error when sending email IP address is not permitted to send messages

I tried to bypass by using VPN software but the SMTP server still sees the non-routable IP. 

The problem still remains, why is my IP address being blocked by Comcast, and how do I get it fixed?

Expert

Re: 421 Error when sending email IP address is not permitted to send messages

 .@

 

Smiley Happy



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I am a Customer Expert volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Mark the post as Best Answer!
Frequent Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

Vthatcher, have you solved your situation yet OR has it gotten WORSE like mine has...now I can't SEND or RECEIVE emails on any of my local POP3 based email programs...

New Poster

Re: 421 Error when sending email IP address is not permitted to send messages

What I've figured out is that Comcast is blocking outgoing emails from the IP address coming from my Verizon router.  I was able to verify that by sending emails from my office computer this morning, which, of course, has a different IP address.

Comcast tech support was supposed to kick my problem up to the next level, but I'm not holding my breath waiting for them to get back to me.  I'm not a current Comcast customer, Comcast is "supporting" previous customers' Comcast email addresses.  I can't help wondering if this is their way of getting rid of me.

I called Verizon this morning about changing my IP address and told that doing a hard reset (red button on back of router) would recycle the DHCP and give me a new IP address.  I will do that when I get home tonight.

Long-term solution is obviously to move to a new email provider, but I need to get back to a functional email first.

Good luck!

Frequent Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

I'm in the same boat - former Comcast customer who was forced to go to Spectrum here in NC when I moved from S. Florida...kept my 4 Comcast email addresses...I too will try to hard reset my modem / router to see what happens...thanks for the thought...

Official Employee

Re: 421 Error when sending email IP address is not permitted to send messages

If you've been unable to resolve the issue thus far, please send me a PM with the error message that you're getting (including the IP).  I'll do my best to get the situation rectified.  To send a PM, click on my name, and then look for a link that says "Private Message".


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New Poster

Re: 421 Error when sending email IP address is not permitted to send messages

Don't know if it's the same issue or not, as I don't get an error message, but my sent emails from the comcast webpage are not being received.  Just the last 2-3 days.

New Poster

Re: 421 Error when sending email IP address is not permitted to send messages

I resolved the issue.  Doing a reset of the router did not change my IP address, as it should have, so I replaced the router at Verizon's suggestion.  Problem solved.

If you have a router that is functioning correctly resetting it should resolve the problem.

Just an FYI, a temporary work-around was to use my Iphone as a Wifi hotspot allowed me to use the Comcast email while I was sorting the router issue.

Good luck to everyone else.

Regular Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

I am having the same problem.  My emails won't send from my Outlook Account although I receive them as usual.  This started Wednesday morning, May 16th.  I've been on the phone countless hours with both Microsoft and Comcast.  My error messages say Sending' reported error (0x800CCC67):' The server responded: 421 resomta-ch2-03v.sys.comcast.net (My IP address) is not permitted to send messages.  Please contact support if you think this is in error.

 

I do have internet service with Frontier but have been paying Comcast separately for the continued use of my comcast email address.

Frequent Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

I have the same exact message please attached.

I've been a Comcast customer for over 20 years, however I had to move to my work ISP, 

I kept comcast emails, I'm able to recieve emails but I can't send, using 2010 Outlook.

I didn't change any thing, tried all the suggested ports, tried Imap and pop.

I can however send emails using Comcast web site.

please help

AK

Frequent Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

I have been having the same problem for a couple of weeks now: An error occurred while sending mail: The mail server sent an incorrect greeting: resomta-ch2-09v.sys.comcast.net resomta-ch2-09v.sys.comcast.net CSI IP xxx.xxx.xxx.xxx is not permitted to send messages. Please contact support if you feel this is in error.. I have contacted Comcast a couple of times and they have escalated the problem a couple of times. A couple of days after the escalation, the problem is solved for some brief period of time and then it re-occurs. The IP address that is not permitted to send messages is different in each episode since I am using a VPN. The problem still exists with the VPN turned off, however. Rebooting the router, turning antivirus off, etc. does not resolve the problem.
Frequent Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

I'm the original poster that started this thread...I'm using a Motorola Surfboard SBG6700-AC modem / router - I'm curious, is anyone else using a Motorola modem / router or some other brand?  Thanks...

Frequent Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

I'm using the Arris modem supplied by Comcast and the Surfboard SB6141 as my router.

Frequent Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

On further testing, I believe that my version of this problem is affected by my VPN.  I use a VPN client that has a "disconnect" and a separate "exit" button.  I thought I was turning the VPN off when I "disconnected" (in this case, I would still get the error message when I tried to send an email).  When I "exit", I do not get the error message and can send email.  I am doing further testing by uninstalling the VPN on one computer and leaving it installed on another to see what I get.  It makes some sense to me that Comcast may be blocking the IP addresses of the VPN servers and, by disabling the VPN, I no longer run afoul of their blocker.

Official Employee

Re: 421 Error when sending email IP address is not permitted to send messages

 

Hi Anon859605, I replied to your original post regarding this issue. Please reach back out to me there for further assistance.

 

 

@aluminum and @Mikeprofla1, if you need additional assistance in getting this error cleared up please send me a private message with your full name, street address, and account number by clicking on my name (ComcastAmir) and then "private message me" and I can check your settings in our back end system. 


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Official Employees are from multiple teams within Comcast: CARE, Product, Leadership. We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Mark the post as Best Answer!
Frequent Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

I believe I have tracked part of my problem to my VPN provider - Private Internet Access.  They reported to me that they have started a whitelist of smtp providers.  What I don't understand (and I am waiting for a response from them) is that they want the IP address of smtp.comcast.net so that they can add it to their whitelist.  Unless I misunderstand, they can get this themselves with a ping. 

With my VPN disconnected (not just 'exited'), I have no problem sending email to either of my SMTP services (comcast and aplus). 

Can someone from Comcast talk with the PIA people?  It's not like Comcast and PIA are mom-and-pop corner stores.  This has got to be a problem for a lot more folks than just me.  PIA says that they have arrangements with other providers of email services to allow SMTP from their servers including AOL, Gmail, Outlook, and Yahoo.  They (PIA) want to block spammers and apparently those other email providers are actively doing something about spammers.  It is not clear to me why Comcast is not included in that group.

 

 

Frequent Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

I replied back with all your suggestions as i noted on my previews respond, I still can't send mail from my Outlook.

please help

Frequent Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

As of now I still can't send emails using my Outlook, I've done everything I was asked to do by you (Comcast Employee).

so far no resoults, It is very frustrating since I'm "not a customer" any more, after being a customer foir 25 years I was hoping for some moreattempt on your part.

Any help ? Any?

AK

Frequent Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

Anon, my problem was finally solved by a knowledgeable Comcast rep on this board...I too am no longer a Comcast customer (which appears to be the source of this problem).  Comcast recently migrated some systems over to new platforms and since my old account number was no longer compatible / valid, I got kicked out of the system.  Once he reset my account, the problem has been fixed!  Hope this helps you...

Regular Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

@ComcastAntiSpam, I have the same issue.  Can you reply to this message so I can send you a private message with the details.  Thanks.

Frequent Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

Otter4, you should be able to go up to the 5/23/2018 posting and follow his instructions on how you can private message him to resolve your problem.  Good luck!

Regular Visitor

Re: 421 Error when sending email IP address is not permitted to send messages


@Mikeprofla1 wrote:

Otter4, you should be able to go up to the 5/23/2018 posting and follow his instructions on how you can private message him to resolve your problem.  Good luck!


I read elsewhere that I am unable to send a private message unless he repies to my post.  I do not get the option to send a private message when I click on his username.  If you can suggest another way I can generate a private message to @ComcastAntiSpam, I am all ears.  Thanks.

Regular Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

Never mind.  This is a UI issue.  I am not shown the button to send a private message until I receive a reply or PM.  When you replied to my post the button appeared.  Thanks for your assitance.  Smiley Happy

Regular Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

I am having the same problem, can you contact me to resolve.

 

Thanks,

Frequent Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

Hi srscharf, hopefully by me replying to your message, a button will appear that will now allow you to send a message to @ComcastAntiSpam, as he was the excellent technician that fixed this problem for me.  Good luck.

Regular Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

Thanks, I was able to make contact and he resolved it.

 

Previously I had 3 online "chats" and 2 telephone calls after escalating the problem with Comcast techs; spending approximately 5 hours of time. I had fully explained the issue, provided the error codes, and none were able to solve it and all said there was nothing Comcast could do!

Frequent Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

Glad to hear it!  This is the experience that everyone has been having - normal techs don't understand the problem nor can they solve it.  You really need a specialist who knows what they're doing.  The guy we've dealt with is the BEST!

New Poster

Re: 421 Error when sending email IP address is not permitted to send messages

I have just started receiving this error message when trying to send email.  Can I get a ticket opened to resolve this?  I recently had to move to another provider (comcast not available in this area) and am not sure if I need to change settings on my end or if comcast changed something on their end.

Frequent Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

Hi mmikesell, hopefully by me replying to your message, a button will appear that will now allow you to send a message to @ComcastAntiSpam, as he was the excellent technician that fixed this problem for me. I actually have the problem AGAIN so I have to do the same today. Good luck.

New Poster

Re: 421 Error when sending email IP address is not permitted to send messages

I am having trouble sending email with me comcast email.  I recently moved and had to chang internet provider.  I was informed that I could keep my comcast email, yet I am receiving an error message whenever I attempt to send email.

Official Employee

Re: 421 Error when sending email IP address is not permitted to send messages

I sent you a private message asking for more details.


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Official Employees are from multiple teams within Comcast: CARE, Product, Leadership. We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Mark the post as Best Answer!
New Poster

Re: 421 Error when sending email IP address is not permitted to send messages

I have been using a Motorola SB6141 modem with Asus RT-AC66U router for a few years and just started having only outbound email issues a few weeks ago.   I have found the root cause of my issue, albeit through my own troubleshooting, since Comcast support is pretty useless...unless you want to try rebooting your router (and wouldn't help in this case anyway.)

 

In order to now get any outgoing message sent from my Outlook 365 mail client I must disconnect my VPN tunnel connection and then click the Send/Receive button in Outlook again after the VPN is off.  Outgoing emails then get sent 100% of the time. 

 

Apparently, the smtp.comcast.mail outgoing mail server has been updated or changed recently and no longer allow customers to send emails with an active VPN connection to the internet.   Try disconnecting any VPN service that you have running and see if that fixes your sending mail issue.

 

This is not a permanent solution but provides me with a workaround to get outgoing emails working despite Comcast Support. 

Regular Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

I am having this problem while at a hotel in Singapore. I've been able to send emails while here; then in the next minute, I cannot send. This is the error message (the comcast server keeps changing):

 

'Your outgoing (SMTP) server does not support SSL-secured connections. If SSL-secured connections have worked in the past, contact your server administrator or Internet service provider (ISP).  The server responded: 421 resomta-ch2-18v.sys.comcast.net resomta-ch2-18v.sys.comcast.net CSI IP 202.55.67.146 is not permitted to send messages.  Please contact support if you feel this is in error.'

 

I have not changed Outlook (2003 version) settings from what I was using when it was working a few minutes before (smtp.comcast.net -- port 465 with SSL and authentification). Chat agent says it's not Xfinity that's blocking me, but what else could the message mean?

Frequent Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

This seems to be similar to my problem but I am not sure as I don't fully understand what is happening.  Here is a link to understanding the 421 SMTP error but it basically says that this error is a general failure: https://www.inmotionhosting.com/support/email/bounceback-errors/email-error-421

 

I would post this as a public response to my posting to show that others are getting similar errors.  Also, send a private message to ComcastAmir (see previous emails in the public thread) as he was at least willing to check it out (whatever that means).  He found no problem with my account settings, forwarded it to the "second tier", who also found no problem.  End of story as far as Comcast is concerned.

 

Hope you can find a solution.  Keep me posted if you do.

Regular Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

I moved to a different location than the hotel. Now emails are sending just fine, with no changes in the Outlook settings. So the issue does appear to be the hotel's IP address -- or the hotel's router that is connecting to the internet?

Official Employee

Re: 421 Error when sending email IP address is not permitted to send messages

I'll try to contact each of you in PM. (the forums weren't notifying me about this thread, I had to re-subscribe, apologies)


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Frequent Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

Here is my current status: The problem still exists. That is, outgoing mail from my Thunderbird client is blocked when my VPN is on. I attempted to change my VPN service from Private Internet Access to NordVPN but experienced the exact same problem. I contacted NordVPN and their response was, "(them) Unfortunately it will not be possible to send emails if your provider is Comcast whilst using a mail client. (me) Why is that? (them) This provider is known not to allow send outgoing mail with VPN." (Exact quote from chat session) The Comcast employee mentioned in a couple of the emails in this thread was very responsive and suggested using another email client since they could see no problem on the Comcast side (even after I pointed out what NordVPN had said which mirrors what Private Internet Access says). I tried SeaMonkey and MailBird and outgoing mail was blocked with both as long as the VPN was active. They both worked fine when the VPN was turned off. I believe I have ruled out anything from the client side of this issue. If there are other suggestions, please don't be shy.
Regular Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

My issue was a blocked IP address on Comcast's side.  was able to unblock the address.

 
Frequent Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

That Comcast employee tried to assist me but found no problem with my account.  They booted it up to tier 2 support who said the same thing.  

 

The IP address that is being blocked is the IP address of the VPN server which can change in order to move the apparent source of the HTML request.  There probably is a block of IP addresses that my VPN vendor (PIA) needs to supply to Comcast so they can be whitelisted.  However, that would allow the evil-doer spammers, who would be using the same servers, to run amok.  At least, that is my understanding at this point. 

New Poster

Re: 421 Error when sending email IP address is not permitted to send messages

I am also having this issue, I can recieve email just fine but i can not send. I am getting the same errors as the others have posted.

Frequent Visitor

Re: 421 Error when sending email IP address is not permitted to send messages

Are you using a VPN?  If so, which one?

New Poster

Re: 421 Error when sending email IP address is not permitted to send messages

No, I'm not using a VPN connection. But I am on a different network. (not comcast)

Official Employee

Re: 421 Error when sending email IP address is not permitted to send messages

@retsel Please click on my UID, and send me a private message with the details of the SMTP response.  I'll see what I can do about it.


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